The present invention concerns a process and a plant for enzymatic inactivation relating to the extraction of puree from food products. The term puree means the pulp of the product in a substantially creamy condition, and then not into pieces, obtained through a strainer which remove the waste matter from the product.
At present, in order to extract puree from food products, generally the product is cold-crushed and then heated with the aim of achieving enzymatic inactivation of the crushed matter which then passes into a strainer or refiner for separating the puree from the waste matter (skins, seeds, stalks, etc.).
When, owing to the particular chemical composition of the processed fruit, there are no significant phenomena involving oxidation, change in colour or separation of liquid parts from solid parts, or when the puree itself is intended for uses where the consistency, colour and separation of solid from liquid are of no importance, in such cases it is possible to perform cold extraction (at room temperature) without any particular precautions during the ensuing heating stage.
In the case, however, of the cold extraction of puree from apples or similar products (such as pears, apricots and peaches, for example) or from products where the loss of consistency, oxidation and separation of solid parts from liquid parts are undesirable phenomena which are to be avoided at all costs, it is necessary to perform enzymatic inactivation immediately in order to avoid such phenomena produced by the pectolytic enzymes.
Cold extraction of the puree ensures optimum quality of the product obtained, and the plant which performs the enzymatic inactivation heat-treatment after extraction must reduce to a minimum the harmful effects (browning, change in taste, etc.) of the high-temperature exposure period on the fresh puree.
At present the plants used for enzymatic inactivation of crushed fruit (and not puree) are also used for the enzymatic inactivation of the cold-extracted puree, but said plants are not suitable for avoiding the abovementioned harmful effects since they are expressly designed so as to ensure long heat: exposure of the product within the plant so that the heat is able to reach the centre of the crushed parts.
In particular said heating is performed by means of a screw with direct steam injection, or with a rotating coil, or by means of a plant of the "pipe-in-pipe" type (in which the product to be heated passes inside one pipe and the heating fluid passes inside the other one, with considerable slowness of the heating process), or else with recirculation of the product within pipe bundles involving the use of a rest tank for heat exposure, in accordance with the configurations schematically illustrated in FIG. 1, which also shows a pipe connecting pipe bundle G and tank F and another pipe on which there are located the inlet and the outlet for the product, a circulation pump H and the instruments necessary for monitoring the process.
With said tank, which is kept at atmospheric pressure or under a slight vacuum to promote evaporation of a small part of liquid present in the crushed fruit, it is possible to obtain enzymatic inactivation and high yields during the following puree extraction stage.
The product enters the recirculation plant (in which there is a pipe bundle where heating takes place) and is mixed by a centrifugal pump, the mechanical action of which, however, may cause an undesirable reduction in the consistency of the puree.
It also necessary to have an extraction pump in order to transfer the heated puree to the next stage.
From IT 1165757 a process and a plant are known for an enzymatic deactivation of chopped product in which the chopped product is introduced into a pressurized and heated (up to over than 100.degree. C.) recirculation circuit.
The drawback is the high temperature and the exposure of the product to high temperatures in the pressurized tank.
In addition to the drawback of the long periods of heat exposure of the product, a further drawback is due to the fact that the traditional plants have stations which are separate and often distant from one another for performing extraction of the puree and carrying out enzymatic inactivation.
Moreover, in traditional plants, after the strainer there is arranged a puree storage tank for supplying a pump which transfers the puree to the plant. This provides the production line with the necessary flexibility since the puree extraction stage and enzymatic inactivation stage are rendered independent to a certain extent by the presence of the tank with the functions of a storage lung. This storage inside the tank is, however, extremely damaging since the puree is at room temperature, the enzymes are active and there is the risk of rapid degradation of the product with gradual oxidation (due to the air which is incorporated during extraction), change in colour and loss of consistency. Moreover, in order to limit these phenomena, use must be made of a significant quantity of inert gas with obvious additional costs, or anti-oxidizing solutions which are also costly and are not liked by the manufacturers of high-quality puree without chemical additives, which is typically used for baby food.